Pressure-sensitive adhesive composition, adhesive sheet, optical film, and image display device

Abstract

To provide a pressure-sensitive adhesive composition capable of forming an adhesive layer with improved adhesion properties, an adhesive sheet comprising an adhesive layer formed from the pressure-sensitive adhesive composition, and an optical film manufactured from the adhesive sheet.SOLUTION: The present invention relates to a pressure-sensitive adhesive composition comprising an acrylic copolymer formed from a polymerizable mixture containing: an alkyl (meth)acrylate monomer with 1 to 12 carbon atoms; an aromatic group-containing (meth)acrylate monomer; a carboxyl group-containing crosslinkable monomer; and a hydroxyl group-containing crosslinkable monomer. The acrylic copolymer has a carbonyl group content of 22.5% to 26.5%, as calculated by formula (1). An adhesive layer formed from the pressure-sensitive adhesive composition exhibits high adhesion to base films and can provide an optical film with enhanced reliability even after prolonged exposure to harsh conditions such as high temperature and high humidity.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, an optical film, and an image display device. [Background technology]

[0002] Adhesives or adhesive sheets can be used to bond display panels of image display devices such as liquid crystal display (LCD) devices and organic light emitting display (OLED) devices to various optical structures or circuit structures, etc. The adhesives must have high adhesive strength as well as improved transparency so as not to deteriorate the optical properties of the image display devices.

[0003] In recent years, displays that have high reliability even under harsh conditions such as high temperature and humidity or under external physical impact have been actively researched. Accordingly, structures that are bonded to the displays must also be formed in a manner that prevents the structures from falling off or peeling off even under harsh conditions or under external impact. Thus, there is a demand for adhesives or adhesive sheets that have high wettability and durability and can bond the display structures.

[0004] For example, Korean Patent Publication No. 2010-0039274 discloses an adhesive for a polarizing plate applied to an image display device. However, conventional known adhesives have limitations in sufficiently securing the above-mentioned properties required for flexible displays. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Korean Patent Publication No. 2010-0039274 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having improved adhesive properties.

[0007] An object of the present invention is to provide a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition, and an optical film produced from the pressure-sensitive adhesive sheet. [Means for solving the problem]

[0008] 1. A pressure-sensitive adhesive composition comprising an acrylic copolymer formed from a polymerizable mixture containing an alkyl (meth)acrylate monomer having 1 to 12 carbon atoms, an aromatic group-containing (meth)acrylate monomer, a carboxy group-containing crosslinkable monomer, and a hydroxy group-containing crosslinkable monomer, wherein the acrylic copolymer has a carbonyl group ratio of 22.5% to 26.5%, and the carbonyl group ratio is calculated by the following formula 1: [Formula 1] JPEG2025085614000002.jpg10125 (in the above formula 1, W k is the content (wt%) of any monomer in the total weight of the polymerizable mixture, and M CO is the molar weight of the carbonyl group (g / mol), and N car、k is the number of carbonyl groups contained in the arbitrary monomer, and M k is the molecular weight (g / mol) of the arbitrary monomer, and n is the number of types of monomers contained in the polymerizable mixture.

[0009] 2. The pressure-sensitive adhesive composition according to item 1, wherein the proportion of the carbonyl groups in the acrylic copolymer is 23% to 26%.

[0010] 3. The pressure-sensitive adhesive composition according to item 1, wherein the alkyl(meth)acrylate monomer having 1 to 12 carbon atoms comprises a first monomer containing an alkyl(meth)acrylate having 1 to 3 carbon atoms and a second monomer containing an alkyl(meth)acrylate having 4 to 12 carbon atoms.

[0011] 4. The pressure-sensitive adhesive composition according to the above item 3, wherein the content of the first monomer is 20% by weight to 45% by weight based on the total weight of the polymerizable mixture.

[0012] 5. The pressure-sensitive adhesive composition according to item 3, wherein the content of the second monomer is 40% by weight to 75% by weight based on the total weight of the polymerizable mixture.

[0013] 6. The pressure-sensitive adhesive composition according to item 1, wherein the aromatic group-containing (meth)acrylate monomer contains an aryloxy group having 6 to 20 carbon atoms.

[0014] 7. A pressure-sensitive adhesive composition according to the above item 1, wherein the aromatic group-containing (meth)acrylate monomer comprises a structure in which an aryl group having 6 to 20 carbon atoms and a (meth)acrylate group are bonded via a polyether segment.

[0015] 8. The pressure-sensitive adhesive composition according to the above item 1, wherein the content of the aromatic group-containing (meth)acrylate monomer is 1 wt % to 15 wt % based on the total weight of the polymerizable mixture.

[0016] 9. The pressure-sensitive adhesive composition according to the above item 1, wherein the content of the carboxy group-containing crosslinkable monomer is 0.01% by weight to 0.5% by weight based on the total weight of the polymerizable mixture.

[0017] 10. The pressure-sensitive adhesive composition according to the above item 1, wherein the content of the hydroxy group-containing crosslinkable monomer is 0.5% by weight to 5% by weight based on the total weight of the polymerizable mixture.

[0018] 11. The pressure-sensitive adhesive composition according to item 1, wherein the ratio of the weight average molecular weight to the number average molecular weight of the acrylic copolymer is 2.5 to 5.

[0019] 12. The pressure-sensitive adhesive composition according to item 1, further comprising at least one additive selected from the group consisting of a crosslinking agent, a silane coupling agent, and an antistatic agent.

[0020] 13. The pressure-sensitive adhesive composition according to item 12, wherein the crosslinking agent is a non-yellowing isocyanate-based crosslinking agent.

[0021] 14. A pressure-sensitive adhesive sheet comprising a base film and an adhesive layer disposed on the base film and formed using the pressure-sensitive adhesive composition according to item 1.

[0022] 15. An optical film comprising: a substrate film; an adhesive layer disposed on an upper surface of the substrate film and formed using the adhesive composition according to item 1; and an antireflection layer disposed on a lower surface of the substrate film.

[0023] 16. An optical film comprising: a base film; an adhesive layer disposed on the base film and formed using the adhesive composition according to item 1; and a protective layer disposed between the base film and the adhesive layer.

[0024] 17. The optical film according to item 15, wherein the base film is a polyvinyl alcohol-based film, and the protective layer is a polymethyl methacrylate-based film.

[0025] 18. An image display device comprising the optical film according to item 15. Effect of the Invention

[0026] The pressure-sensitive adhesive composition according to an exemplary embodiment of the present invention may include an acrylic copolymer containing an appropriate number of carbonyl groups, which can improve the chemical stability of the pressure-sensitive adhesive composition and can improve the durability of the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition in harsh environments.

[0027] The adhesive sheet according to the exemplary embodiment of the present invention can have a uniform light transmittance, thereby improving the light leakage phenomenon and improving the quality of an image display device including the adhesive sheet. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a pressure-sensitive adhesive sheet according to an exemplary embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view illustrating a pressure-sensitive adhesive sheet according to an exemplary embodiment. [Diagram 3] FIG. 3 is a schematic cross-sectional view illustrating an optical film according to an exemplary embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view for explaining an image display device according to an exemplary embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] According to an embodiment of the present invention, there is provided a pressure-sensitive adhesive composition including an acrylic copolymer having an appropriate number of carbonyl groups. Also provided is a pressure-sensitive adhesive sheet and an optical film including a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition.

[0030] The present invention will now be described in detail.

[0031] <Adhesive composition> The pressure-sensitive adhesive composition according to an exemplary embodiment may include an acrylic copolymer formed from a polymerizable mixture including an alkyl (meth)acrylate monomer having 1 to 12 carbon atoms, an aromatic group-containing (meth)acrylate monomer, a carboxy group-containing crosslinkable monomer, and a hydroxy group-containing crosslinkable monomer.

[0032] As used herein, the term "(meth)acrylate" is used in a manner that encompasses acrylate or methacrylate.

[0033] The alkyl (meth)acrylate monomer having 1 to 12 carbon atoms may include a first alkyl (meth)acrylate monomer having 1 to 3 carbon atoms and a second alkyl (meth)acrylate monomer having 4 to 12 carbon atoms. According to an exemplary embodiment, the polymerizable mixture includes both the first monomer and the second monomer, thereby realizing improved adhesive strength and preventing defects in the adhesive sheet even in high temperature and / or high humidity environments.

[0034] The first monomer and the second monomer may each be a compound derived from an aliphatic alcohol having 1 to 12 carbon atoms.

[0035] Examples of the first monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, etc., and preferably methyl (meth)acrylate. These may be used alone or in combination of two or more.

[0036] In some embodiments, the content of the first monomer may be 20 to 45 wt %, and preferably 20 to 40 wt %, based on the total weight of the polymerizable mixture, which can sufficiently improve the adhesive strength and heat resistance of the adhesive sheet.

[0037] Examples of the second monomer include n-butyl (meth)acrylate, 2-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, etc. The second monomer may be preferably n-butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate. These may be used alone or in combination of two or more.

[0038] In some embodiments, the content of the second monomer may be 40 to 75 wt % based on the total weight of the polymerizable mixture, and preferably 45 to 70 wt %. Within this range, it is possible to prevent a decrease in the cohesive strength of the pressure-sensitive adhesive composition, which would otherwise cause a decrease in the durability of the pressure-sensitive adhesive layer, and to improve the crosslink density and adhesive strength of the pressure-sensitive adhesive layer.

[0039] In exemplary embodiments, the ratio of the content of the second monomer to the content of the first monomer in the total weight of the polymerizable mixture may be 1 to 3. In some embodiments, the ratio of the content of the second monomer to the content of the first monomer in the total weight of the polymerizable mixture may be 1.2 to 2.7.

[0040] Within this range, the content of the second monomer having a longer alkyl group is equal to or greater than the content of the first monomer, thereby improving the heat resistance of the pressure-sensitive adhesive sheet.

[0041] According to an exemplary embodiment, the polymerizable mixture may include an aromatic group-containing (meth)acrylate monomer. This allows the acrylic copolymer to include a bulky aromatic group with high heat resistance, thereby improving the durability of the pressure-sensitive adhesive sheet in harsh environments. In addition, the acrylic copolymer formed from the polymerizable mixture including the aromatic group-containing (meth)acrylate monomer may improve the refractive index of the pressure-sensitive adhesive composition, thereby improving the light leakage phenomenon.

[0042] According to an exemplary embodiment, the aromatic group of the aromatic group-containing (meth)acrylate monomer may include an aryl group having a carbon number of 6 to 20. The aryl group is a hydrocarbon group including at least one aromatic ring, and may include, for example, a phenyl group, a biphenyl group, a naphthalene group, and the like.

[0043] According to an exemplary embodiment, the aromatic group-containing (meth)acrylate monomer may include an aryloxy group having 6 to 20 carbon atoms. The aryloxy group may refer to a group in which an aryl group is bonded to an oxygen atom. For example, the aryloxy group may include a phenoxy group, a biphenyloxy group, a naphthaleneoxy group, etc.

[0044] According to an exemplary embodiment, the aromatic group-containing (meth)acrylate monomer may include a structure in which a (meth)acrylate group is bonded to an aryloxy group having 6 to 20 carbon atoms via an alkylene group linker.

[0045] According to some embodiments, the aromatic group-containing (meth)acrylate monomer may include a structure in which an aryl group having 6 to 20 carbon atoms and a (meth)acrylate group are bonded via a polyether segment. The term "polyether segment" refers to a divalent oxyalkylene repeating unit (-O-(CH 2 ) m -)。 Linker structure containing.

[0046] The aromatic group-containing (meth)acrylate monomer can be represented by the following Chemical Formula 1.

[0047] [ka]

[0048] In the above formula 1, Ar is an aryl group having 6 to 20 carbon atoms, and R 1 is an alkylene group having 1 to 5 carbon atoms, and R 2 is a hydrogen atom or a methyl group, and m is an integer of 1 to 10.

[0049] Examples of the aromatic group-containing (meth)acrylate monomer include phenoxymethyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, biphenyloxymethyl (meth)acrylate, biphenyloxyethyl (meth)acrylate, biphenyloxypropyl (meth)acrylate, phenoxyethoxyethyl (meth)acrylate, and phenoxyethoxyethoxyethyl (meth)acrylate. The aromatic group-containing (meth)acrylate monomer may preferably be phenoxyethyl (meth)acrylate. These may be used alone or in combination of two or more.

[0050] According to an exemplary embodiment, the content of the aromatic group-containing (meth)acrylate monomer may be 1 wt% to 15 wt% based on the total weight of the polymerizable mixture. According to some embodiments, the content of the aromatic group-containing (meth)acrylate monomer may be 5 wt% to 10 wt% based on the total weight of the polymerizable mixture. In the above range, the refractive index can be controlled without decreasing the adhesive properties, and a light compensation function against light leakage can be imparted.

[0051] The carboxy group-containing crosslinkable monomer and the hydroxy group-containing crosslinkable monomer each contain a carboxy group or a hydroxy group that may be contained in a form bonded to a copolymer chain, and may contain a crosslinkable group that can form a copolymer by polymerization reaction with the (meth)acrylate monomer.

[0052] The carboxyl group-containing crosslinkable monomer can impart adhesive strength to the pressure-sensitive adhesive composition. For example, the acrylic copolymer can improve the adhesion and crosslinking degree of the pressure-sensitive adhesive composition by having an acidic group derived from the carboxyl group-containing monomer.

[0053] Examples of the carboxy-containing crosslinkable monomer include acrylic acid, methacrylic acid, etc. These may be used alone or in combination of two or more.

[0054] The content of the carboxyl group-containing crosslinkable monomer may be 0.01% by weight to 0.5% by weight based on the total weight of the polymerizable mixture, for example, the content of the carboxyl group-containing crosslinkable monomer may be 0.1% by weight to 0.5% by weight based on the total weight of the polymerizable mixture.

[0055] When the content of the carboxy group-containing crosslinkable monomer is within the above range, the adhesive strength of the adhesive sheet formed from the adhesive composition can be appropriately improved, and migration of the ionic antistatic agent described below to the surface of the adhesive sheet can be prevented.

[0056] The hydroxyl group-containing crosslinkable monomer can impart a highly polar hydroxyl group to the acrylic copolymer, thereby enhancing the adhesive strength of the acrylic copolymer to a polar substrate.

[0057] Examples of the hydroxyl group-containing crosslinkable monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, 2-hydroxypropylene glycol (meth)acrylate, hydroxyalkylene glycol (meth)acrylate having an alkylene group with 2 to 4 carbon atoms, 4-hydroxybutyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, 7-hydroxyheptyl vinyl ether, 8-hydroxyoctyl vinyl ether, 9-hydroxynonyl vinyl ether, and 10-hydroxydecyl vinyl ether. These may be used alone or in combination of two or more.

[0058] In some embodiments, the content of the hydroxyl group-containing crosslinkable monomer may be 0.5% by weight to 5% by weight based on the total weight of the polymerizable mixture, for example, the content of the hydroxyl group-containing crosslinkable monomer may be 0.5% by weight to 4% by weight based on the total weight of the polymerizable mixture.

[0059] In some embodiments, in addition to the monomer, other polymerizable monomers known in the art may be used in an amount not decreasing the adhesive strength. For example, the other polymerizable monomers may be further included in an amount of 10 wt % or less based on the total weight of the polymerizable mixture.

[0060] The method for producing the acrylic copolymer is not particularly limited, and may be a method commonly used in the art, such as bulk polymerization, solution polymerization, emulsion polymerization, or suspension polymerization, preferably a solution polymerization method. In addition, a solvent, a polymerization initiator, a chain transfer agent for controlling molecular weight, and the like commonly used in polymerization may be used.

[0061] In exemplary embodiments, the acrylic copolymer may have a carbonyl group percentage of 22.5% to 26.5%. In some embodiments, the acrylic copolymer may have a carbonyl group percentage of 23% to 26%.

[0062] The proportion of carbonyl groups is calculated by the following formula 1. [Formula 1] JPEG2025085614000004.jpg10125

[0063] In the above formula 1, W k is the content (wt%) of any monomer in the total weight of the polymerizable mixture, and M CO is the molar weight of the carbonyl group (g / mol), and N car、k is the number of carbonyl groups contained in the arbitrary monomer, and M k is the molecular weight (g / mol) of the arbitrary monomer, and n is the number of types of monomers contained in the polymerizable mixture.

[0064] Said M CO is the molar weight of the carbonyl group (-C(=O)-), which is the sum of the atomic weights of the carbon and oxygen atoms, and may have a value of about 28 g / mol.

[0065] The ratio of carbonyl groups calculated by the formula 1 may be the ratio of the total weight of carbonyl groups contained in the acrylic copolymer to the total weight of the acrylic copolymer. Further, the n may be 4 or more, for example, 4 to 20.

[0066] The proportion of carbonyl groups can be calculated as the sum of values ​​obtained by multiplying the weight ratio of carbonyl groups in the weight of each of all monomers contained in the polymerizable mixture by the content of each monomer in the total weight of the polymerizable mixture.

[0067] Moreover, the acrylic copolymer can satisfy the following formula 2.

[0068] [Formula 2] JPEG2025085614000005.jpg1040

[0069] If the proportion of carbonyl groups in the acrylic copolymer is less than 22.5%, the adhesive strength of the adhesive sheet may decrease excessively, whereas if it exceeds 26.5%, the heat resistance and moist heat resistance of the adhesive sheet may decrease, resulting in a decrease in adhesive quality.

[0070] In an exemplary embodiment, the weight average molecular weight (polystyrene equivalent, Mw) of the acrylic copolymer may be 50,000 to 2,000,000, and preferably 400,000 to 2,000,000, 1,000,000 to 2,000,000, or 1,200,000 to 1,600,000. For example, the weight average molecular weight can be measured by gel permeation chromatography (GPC).

[0071] In some embodiments, the number average molecular weight (Mn) of the acrylic copolymer may be 200,000 to 1,000,000, preferably 250,000 to 800,000, or 300,000 to 500,000.

[0072] Within this range, the gel fraction of the pressure-sensitive adhesive composition can be adjusted to an appropriate level, the cohesive force between the copolymers is sufficient, and the durability of the pressure-sensitive adhesive sheet can be ensured.

[0073] According to an exemplary embodiment, the ratio of the weight average molecular weight to the number average molecular weight of the acrylic copolymer may be 2.5 to 5. According to some embodiments, the ratio of the weight average molecular weight to the number average molecular weight of the acrylic copolymer may be 2.8 to 4. Within this range, the heat resistance of the pressure-sensitive adhesive sheet can be further improved.

[0074] In an exemplary embodiment, the pressure-sensitive adhesive composition may further include a crosslinking agent, a silane coupling agent, an antistatic agent, and the like.

[0075] The crosslinking agent can improve the cohesive strength, adhesion and high temperature reliability of the adhesive, and can play a role in maintaining the shape of the adhesive.

[0076] In some embodiments, the crosslinking agent may be a non-yellowing isocyanate-based crosslinking agent. The term "yellowing isocyanate-based crosslinking agent" refers to a compound in which a phenyl carbon is directly linked to a nitrogen atom of an isocyanate among isocyanate-based crosslinking agents. The term "non-yellowing isocyanate-based crosslinking agent" refers to the remainder of the isocyanate-based crosslinking agents excluding the yellowing isocyanate-based crosslinking agents.

[0077] The non-yellowing type crosslinking agent may include an isocyanate-based compound or an aziridine-based compound, which has high reactivity with polar functional groups and can have improved adhesion to a substrate film that has been corona discharge-treated or plasma-treated.

[0078] Examples of the non-yellowing type isocyanate compound include diisocyanate compounds such as xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and tetramethyl xylylene diisocyanate; an adduct in which 1 equivalent of a polyhydric alcohol compound such as trimethylolpropane is reacted with 3 equivalents of a diisocyanate compound; an isocyanurate body in which 3 equivalents of a diisocyanate compound are self-condensed; a biuret body in which 1 equivalent of diisocyanate is condensed with the remaining diisocyanate, obtained from 2 equivalents of the 3 equivalents of a diisocyanate compound; and polyfunctional isocyanate compounds containing three functional groups, such as triphenylmethane triisocyanate and methylene bis triisocyanate. These can be used alone or in combination of two or more.

[0079] Examples of the aziridine-based compound include pentaerythritol-tris-(β-(N-aziridinyl)propionate, trimethylolpropane-tris(β-N-aziridinyl)propionate, trimethylolpropane tris(2-methyl-1-aziridinepropionate), N,N'-toluene-2,4-bis(1-aziridinecarboxamide), N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), triethylenemelamine, bisisoptaloyl-1-(2-methylaziridine), and tri-1-aziridinylphosphine oxide. These may be used alone or in combination of two or more.

[0080] In some embodiments, the content of the crosslinking agent may be 0.1 to 3 parts by weight, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the acrylic copolymer. In this range, the acrylic copolymer can be appropriately crosslinked to improve the cohesive strength, thereby improving the adhesive durability and cuttability of the pressure-sensitive adhesive sheet, and the residual stress can be maintained at an appropriate level to ensure adhesion to the adherend.

[0081] The silane coupling agent forms a covalent bond or a hydrogen bond with a functional group present on the surface of an adherend, thereby preventing lifting and peeling of the adhesive layer formed from the adhesive composition and improving adhesive strength.

[0082] The silane coupling agent may include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyldimethylmethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyldimethylethoxysilane, etc. These may be used alone or in combination of two or more.

[0083] In some embodiments, the content of the silane coupling agent may be 0.1 to 3 parts by weight, and preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the acrylic copolymer.

[0084] The antistatic agent may be an ionic antistatic agent. The ionic antistatic agent may contain an ionic salt composed of an anion and a cation, and may impart ionic conductivity to the adhesive layer formed from the adhesive composition. For example, the surface resistivity of the adhesive layer may be 10×10 10 It may be Ω / □ or less, and preferably 7×10 10 It may be Ω / □ or less.

[0085] In some embodiments, the ionic antistatic agent can include an alkali metal salt, an ionic liquid, or an ionic solid, preferably an ionic solid.

[0086] By including an ionic solid as an ionic antistatic agent, the stability of the pressure-sensitive adhesive composition over time and the durability of the pressure-sensitive adhesive layer can be improved. In addition, the ionic solid has high compatibility with the other components described above, and can maintain high transparency of the pressure-sensitive adhesive composition.

[0087] In some embodiments, the melting point of the ionic solid may be 20° C. or higher, specifically 20° C. to 50° C. In this case, the mobility of the ionic solid is minimized, and the durability and reliability of the adhesive sheet or optical film can be improved. For example, if the melting point of the ionic solid is less than 20° C., the fluidity of the ionic solid increases, and the ionic solid may move to the edge of the adhesive sheet or optical film and dissolve.

[0088] In some embodiments, the ionic solid contains Cl as the anion. - , Br - , I - , AlCl 4 - , Al 2 Cl 7 - , B.F. 4 - , P.F. 6 - , ClO 4 - , NO 3 - , CO 3 2- , C.H. 3 COO - , C.F. 3 COO - , C.H. 3 SO 3 - , C.F. 3 SO 3 - , (FSO 2 ) 2 N - , (CF3 SO 2 ) 2 N - , (CF 3 SO 2 ) 3 C - , AsF 6 - , SbF 6 - , NbF 6 - , TaF 6 - , F(HF) n - , (CN) 2 N - , C 4 F 9 SO 3 - , (C 2 F 5 SO 2 ) 2 N - , C 3 F 7 COO - , C 6 H 5 COO - , (CF 3 SO 2 )(CF 3 CO)N - , OTF - (trifluoromethanesulfonate), OTs - (toluenesulfonate), OMs - (methanesulfonate), and / or BPh 4 - (tetraphenylborate) and the like.

[0089] In some embodiments, the ionic solid can include as a cation imidazolium, pyridinium, alkylammonium, alkylpyrrolidinium, and / or alkylphosphonium.

[0090] In some embodiments, the content of the ionic antistatic agent may be 0.01 to 5 parts by weight based on 100 parts by weight of the acrylic copolymer. Within this range, the antistatic properties of the adhesive layer are improved, and the durability of the adhesive layer can be maintained at an excellent level.

[0091] The pressure-sensitive adhesive composition may further include additives known in the art to adjust adhesive strength, cohesive strength, viscosity, elastic modulus, glass transition temperature, etc., as required depending on the application. For example, the pressure-sensitive adhesive composition may include, as additives, a tackifier, an antioxidant, a corrosion inhibitor, a leveling agent, a surface lubricant, a dye, a pigment, an antifoaming agent, a filler, a light stabilizer, a plasticizer, etc.

[0092] <Adhesive sheet> Hereinafter, the embodiments of the present invention will be described in more detail with reference to the drawings. However, the drawings attached to this specification are intended to illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to aid in further understanding of the technical concept of the present invention, and therefore the present invention should not be interpreted as being limited only to the matters depicted in the drawings.

[0093] FIG. 1 is a schematic cross-sectional view showing a pressure-sensitive adhesive sheet according to an exemplary embodiment.

[0094] Referring to FIG. 1 , an adhesive sheet according to an exemplary embodiment may include a base film 110, an adhesive layer 120 disposed on the upper surface of the base film 110, and a release film 130 disposed on the upper surface of the adhesive layer 120.

[0095] The adhesive layer 120 can be formed from the above-mentioned adhesive composition. For example, the adhesive layer 120 can be formed by applying an adhesive composition containing an acrylic copolymer onto the base film 110 and curing it.

[0096] In some embodiments, the base film 110 may include an acrylic resin, a cellulose resin, a polyolefin resin, a polyester resin, etc. In this case, the transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. of the base film 110 may be improved.

[0097] For example, the base film 110 may include acrylic resins such as polymethyl (meth)acrylate and polyethyl (meth)acrylate; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene isophthalate, polyethylene naphthalate and polybutylene naphthalate; cellulose resins such as diacetyl cellulose, triacetyl cellulose and cellulose acetate butylene; polyolefin resins such as polyethylene, polypropylene, cycloolefin, polyolefin having a norbornene structure and ethylene-propylene copolymer; sulfone resins; polyether-ether ketone resins; arylate resins; or mixtures of the above resins.

[0098] In one embodiment, at least one surface of the base film 110, for example, the surface on which the adhesive layer 120 is formed, can be surface-treated. For example, one surface of the base film 110 can be subjected to corona discharge treatment, plasma treatment, blast treatment, primer treatment, or the like.

[0099] The surface treatment can generate a carboxylic acid derivative (R-COOH) on the surface of the base film 110. The carboxyl group of the carboxylic acid derivative can react with the pressure-sensitive adhesive composition, thereby further improving the adhesion of the pressure-sensitive adhesive layer to the base film.

[0100] In one embodiment, the surface of the substrate film 110 may not be saponified. In this case, the adhesive strength of the substrate film may be deteriorated. Since the substrate film used in the adhesive sheet has a hydrophobic surface, the adhesive strength between the substrate and the adhesive can be improved by performing a pretreatment process of saponification by immersing the substrate in an alkaline aqueous solution, forming a separate coating layer between the substrate and the adhesive, or by corona or plasma treatment of the substrate film surface.

[0101] However, when a saponification process is performed or a separate coating layer is formed, the process becomes complicated, which may reduce the yield and processability of the adhesive sheet, and the additional pretreatment or coating layer formation process may cause contamination and deterioration of the quality of the adhesive sheet.

[0102] The adhesive layer 120 can be formed by applying the above-mentioned adhesive composition onto at least one surface of the base film 110, and drying and / or curing the composition. For example, the adhesive layer 120 can be formed by applying the adhesive composition onto the base film 110 by a coating method such as roll coating, gravure coating, reverse coating, spray coating, air knife coating, or die coating.

[0103] According to an exemplary embodiment, the gel fraction of the adhesive layer 120 may be 60% to 80%, and preferably 65% ​​to 75%. The gel fraction of the adhesive layer 120 can be calculated by the following Equation 3.

[0104] [Formula 3] JPEG2025085614000006.jpg1077

[0105] In formula 3, W1 may be the initial weight of the adhesive layer, and W2 may be the weight measured after the adhesive layer is immersed in an ethyl acetate solution at room temperature for 3 days and dried at 120° C. for 24 hours.

[0106] Within this range, the crosslinking degree and cohesive strength of the adhesive layer 120 are increased, so that the durability over time and reworkability can be improved, and the durability and adhesion of the adhesive layer 120 can be improved.

[0107] The adhesive sheet may further include a release film 130 disposed on one surface of the adhesive layer 120. For example, the adhesive sheet may include a base film 110, an adhesive layer 120, and a release film 130 disposed in that order.

[0108] In some embodiments, the pressure-sensitive adhesive sheet may be provided in a form in which a base film 110 and a release film 130 are attached to both sides.

[0109] 2 is a schematic cross-sectional view illustrating an adhesive sheet according to an exemplary embodiment. Referring to FIG. 2, when the adhesive sheet is used, the release film 130 can be removed from the adhesive sheet. In this case, the release film 130 is removed from the adhesive sheet, and the exposed adhesive layer 120 can be attached to an object to be adhered (e.g., a display panel).

[0110] In some embodiments, the adhesive sheet may be provided in a form in which release films 130 are attached to both sides of the adhesive layer 120 .

[0111] For example, the release film 130 attached to one side of the adhesive sheet can be removed, and the optical substrate film 110 or a functional layer (e.g., an anti-reflection layer) can be attached to the exposed surface of the adhesive layer 120 to form a laminate.

[0112] In one embodiment, the anti-reflective layer may be provided as an anti-reflective plate attached to one side of the optical substrate film 110, or may be attached onto the other side of the optical substrate film 110 to which the adhesive layer 120 of the adhesive sheet is attached.

[0113] <Optical films, image display devices> FIG. 3 is a schematic cross-sectional view illustrating an optical film according to an exemplary embodiment.

[0114] Referring to FIG. 3, the optical film may include a base film 110, an adhesive layer 120 disposed on one side of the base film 110, and an optical functional layer 140 disposed on the other side of the base film 110.

[0115] For example, the optical film can be produced by forming an optical functional layer 140 on one side of a base film 110, and then applying and curing an adhesive composition on the other side of the base film 110 to form an adhesive layer 120.

[0116] In some embodiments, the optical functional layer 140 can include an anti-reflection layer, a hard coat layer, a retardation layer, etc. For example, the optical film can be provided as an anti-reflection film, a hard coat film, a window film, a retardation film, etc., depending on the optical functional layer 140.

[0117] An optical film according to some embodiments may include a substrate film, an adhesive layer disposed on the substrate film and formed using the adhesive composition, and a protective layer disposed between the substrate film and the adhesive layer.

[0118] In one embodiment, the optical film may include a substrate film, a polarizing plate including a protective layer disposed on the substrate film, and an adhesive layer disposed on the polarizing plate and in contact with the protective layer.

[0119] The substrate film may be a polarizer, for example, a polyvinyl alcohol film.

[0120] The protective layer can be disposed between the base film and the adhesive layer. In some embodiments, the optical film can include protective layers disposed on both sides of the base film. In this case, the adhesive layer can be disposed on either of the protective layers.

[0121] The protective layer may include, for example, polymethyl methacrylate (PMMA), triacetyl cellulose (TAC), etc. In some embodiments, the optical film may further include a release film disposed on one side of the adhesive layer 120. For example, the optical film may be provided in a form in which the base film 110 and the release film are attached to both sides of the adhesive layer 120. In this case, the release film formed on one side of the adhesive layer 120 may be removed, and the exposed surface of the adhesive layer 120 may be attached to a target object (e.g., a display panel).

[0122] In some embodiments, when release films 130 are attached to both sides of the adhesive layer 120, the release film 130 on one side can be removed and then the optical functional layer 140 can be attached to the exposed surface, and the release film 130 remaining on the other side of the adhesive layer 120 can be removed and then an object (e.g., a display panel) can be attached to the exposed surface.

[0123] FIG. 4 is a schematic cross-sectional view for explaining an image display device according to an exemplary embodiment.

[0124] Referring to FIG. 4, the image display device may include a display panel 200 and an optical film disposed on the display panel 200 .

[0125] In some embodiments, the image display device may include a display panel 200 and an optical film disposed on the upper surface of the display panel via an adhesive layer 120. For example, the release film 130 is removed from the optical film, and the exposed adhesive layer 120 is attached to the display panel 200, thereby providing the image display device.

[0126] The display panel 200 may be a liquid crystal display panel (LCD), an organic light emitting display panel (OLED), or a quantum dot light emitting display panel (QLED).

[0127] In addition to the above components, the image display device may further include other components known in the art, such as a retardation film, a hard coat film, a protective film, a window film, a touch panel, etc. The above components may be attached to each other by the adhesive composition according to the exemplary embodiment.

[0128] As described above, improved durability and stability can be obtained by improving the adhesion and bonding between the base film 110 and the adhesive layer 120. Therefore, even when subjected to physical external forces such as repeated bending or under harsh conditions such as high temperature and high humidity, the adhesive reliability of the image display device can be maintained for a long period of time, and the phenomena of breakage, peeling, and lifting of each component can be prevented.

[0129] In addition, even after long periods of exposure to harsh conditions such as high temperature and humidity, the adhesive sheet can be peeled off without damaging the target object during rework or leaving any adhesive residue.

[0130] Below, preferred embodiments are presented to aid in understanding the present invention. However, these embodiments are merely illustrative of the present invention and do not limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications to the embodiments are possible within the scope of the scope and technical spirit of the present invention, and it is natural that such changes and modifications fall within the scope of the appended claims.

[0131] Manufacturing Example Production Example 1: Production of acrylic copolymer (A-1) In a 1L reactor equipped with a cooling device for easy temperature control and refluxing nitrogen gas, a polymerizable mixture (65.8% by weight of n-butyl acrylate (BA), 25% by weight of methacrylate (MA), 8% by weight of phenoxyethyl acrylate (PEA), 0.2% by weight of acrylic acid (AA), and 1% by weight of 2-hydroxyethyl acrylate (2-HEA) was added, followed by 100 parts by weight of ethyl acetate (EA) as a solvent. After that, nitrogen gas was added for 1 hour to remove oxygen, and the temperature was maintained at 62°C. After the mixture was stirred uniformly, 0.07 parts by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator and reacted for 8 hours to produce an acrylic copolymer (A-1).

[0132] Production Examples 2 to 13: Production of acrylic copolymers (A-2) to (A-13) An acrylic copolymer was produced in the same manner as in Production Example 1, except that a polymerizable mixture composed of the components and amounts shown in Table 1 below was used.

[0133] [Table 1] M-1: Methyl acrylate M-2: n-butyl acrylate M-3: Phenoxyethyl acrylate M-4: Phenoxyethoxyethoxyethyl acrylate M-5: Acrylic acid M-6: 2-Hydroxyethyl acrylate

[0134] Experimental Example 1: Calculation of the carbonyl group ratio In the acrylic copolymers of Production Examples 1 to 17, the proportion of carbonyl groups was calculated according to the above formula 1. For example, the acrylic copolymer of Production Example 1 was produced from a polymerizable mixture containing five types of monomers, and the proportion of carbonyl groups can be calculated to be 23.91% using Equation 1 from the values ​​shown in Table 2 below.

[0135] [Table 2]

[0136] The proportions of carbonyl groups in the acrylic copolymers of Production Examples 2 to 17 were calculated in a similar manner.

[0137] Experimental Example 2: Molecular weight measurement Gel permeation chromatography (GPC) was used to measure the weight average molecular weight (polystyrene equivalent, Mw) and number average molecular weight (Mn) of the acrylic copolymers of Production Examples 1 to 17. The ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) was also calculated.

[0138] [Table 3]

[0139] Examples and Comparative Examples (1) Production of adhesive composition The acrylic copolymer (A), crosslinking agent (B), silane coupling agent (C) and antistatic agent (D) were mixed in the amounts and components shown in Table 4 below, and then diluted with ethyl acetate to a solid content of about 15% by weight to prepare pressure-sensitive adhesive compositions of the Examples and Comparative Examples. The content unit of each component in the table below is parts by weight relative to 100 parts by weight of the acrylic copolymer.

[0140] (2) Manufacturing of adhesive sheets The prepared adhesive composition was applied onto a release film coated with a silicone release agent and dried at 100°C for 2 minutes to form an adhesive layer with a thickness of 20 μm. A polarizing plate was laminated as a base film onto the formed adhesive layer to prepare an adhesive sheet. The polarizing plate was an iodine-based polarizing plate (thickness 185 μm) in which a corona-discharge-treated polymethyl methacrylate (PMMA) film was laminated on one side of a polyvinyl alcohol (PVA) polarizer and a triacetyl cellulose (TAC) film was laminated on the other side. The corona-discharge-treated PMMA film surface was laminated so as to be in contact with the adhesive layer.

[0141] [Table 4]

[0142] (A) Acrylic copolymer A-1: Copolymer prepared in Preparation Example 1 A-2: Copolymer prepared in Preparation Example 2 A-3: Copolymer prepared in Preparation Example 3 A-4: Copolymer prepared in Preparation Example 4 A-5: Copolymer prepared in Preparation Example 5 A-6: Copolymer prepared in Preparation Example 6 A-7: Copolymer prepared in Preparation Example 7 A-8: Copolymer prepared in Preparation Example 8 A-9: Copolymer prepared in Preparation Example 9 A-10: Copolymer prepared in Preparation Example 10 A-11: Copolymer prepared in Preparation Example 11 A-12: Copolymer prepared in Preparation Example 12 A-13: Copolymer prepared in Preparation Example 13 A-14: Copolymer prepared in Preparation Example 14 A-15: Copolymer prepared in Preparation Example 15 A-16: Copolymer prepared in Preparation Example 16 A-17: Copolymer prepared in Preparation Example 17 (B) Crosslinking agent B-1: D-110N (xylene diisocyanate crosslinking agent, manufactured by Mitsui Chemicals) B-2: Coronate-HXR (hexamethylene diisocyanate crosslinking agent, manufactured by Nippon Polyurethane Industry Co., Ltd.) B-3: D-120N (hydrogenated xylylene diisocyanate crosslinking agent, manufactured by Mitsui Chemicals) B-4: Coronate-L (Nippon Polyurethane Industry Co., Ltd.) (C) Silane coupling agent 3-Glycidoxypropyltrimethoxysilane (Shin-Etsu Chemical) (D) Antistatic agent 1-Octyl-4-methylpyridinium hexafluorophosphate (Kyoei Chemical Co., Ltd.)

[0143] Experimental Example 3: Evaluation of Adhesion The manufactured adhesive sheet was cut into a size of 25mm x 50mm, and the base film surface was fixed to a plate made of stainless steel using double-sided tape. The adhesive layer surface was moved back and forth 20 times in the short side direction using elastic rubber at a pressure of 1MPa and a speed of 0.1m / s. The distance the adhesive layer was pushed out on the base film was measured to determine the adhesion.

[0144] Experimental Example 4: Measurement of adhesive strength The produced adhesive sheet was cut to a length of 25 mm and a width of 100 mm, and the release film was peeled off. The exposed adhesive layer was then attached to a glass substrate (#1737, Corning Incorporated material) and autoclaved at a temperature of 50°C and a pressure of 5 atmospheres for 20 minutes to prepare a test specimen.

[0145] To measure the room temperature adhesive strength, the test piece prepared above was left for 24 hours under conditions of 23°C temperature and 50% RH. Using a universal tensile tester (UTM, manufactured by Instron), the adhesive sheet was peeled from the glass substrate at a peeling speed of 300 mm / min and a peeling angle of 180° to measure the room temperature adhesive strength.

[0146] Experimental Example 5: Evaluation of durability The prepared adhesive sheet was cut to a length of 200 mm x width of 300 mm, the release film was peeled off, and the exposed adhesive layer was attached to a glass substrate (210 mm x 350 mm x 0.7 mm) and autoclaved (0.5 MPa) at a temperature of 50°C for 30 minutes to prepare a test specimen. The pressure applied during the attachment was 5 kg / cm. 2 It was.

[0147] Heat resistance was evaluated by leaving the test pieces at a temperature of 80°C or 95°C for 1000 hours and then observing the occurrence of bubbles or peeling.

[0148] The moist heat resistance was evaluated by leaving the test pieces for 1000 hours under conditions of 60°C and 90% RH or 65°C and 95% RH, and then observing the occurrence of bubbles or peeling. Before evaluating the condition of the test pieces after leaving them under high temperature and high humidity, the test pieces were left for 24 hours at room temperature and then observed.

[0149] <Evaluation criteria> ◎: No bubbles or peeling ○: Air bubbles or peeling <5 pieces △: 5 pieces or less bubbles or peeling < 10 pieces X: 10 or less bubbles or peeling

[0150] Experimental Example 6: Evaluation of light leakage prevention In order to check the uniformity of light transmittance using the same test piece as above, a backlight was used to observe whether there were any areas where light leaked in a dark room. Specifically, the test piece (200 mm x 200 mm) was crossed at 90° and attached to both sides of a glass substrate (210 mm x 210 mm x 0.7 mm) and observed. The uniformity of light transmittance was evaluated according to the following criteria.

[0151] <Evaluation criteria> ○: No light leakage spots are visually observed or only weakly observed △: Light leakage spots are clearly visible X: Excessive light leakage spots are observed

[0152] [Table 5]

[0153] Referring to Tables 3 to 5, the adhesive composition of the embodiment containing the acrylic copolymer having a carbonyl group ratio of 22.5 to 26.5% provided an adhesive sheet having high adhesive strength and improved heat resistance and moist heat resistance. In addition, the light leakage phenomenon of the adhesive sheet was reduced, and an image display device with improved quality was provided.

[0154] What has been described is merely illustrative of the application of the principles of the present disclosure and other arrangements may be included without departing from the scope of the present invention. [Explanation of symbols]

[0155] 110: Base film 120: Adhesive layer 130: Release film 140: Optical functional layer 200: Display panel

Claims

1. an alkyl (meth)acrylate monomer having 1 to 12 carbon atoms; an aromatic group-containing (meth)acrylate monomer; a carboxy group-containing crosslinkable monomer; and a hydroxyl group-containing crosslinkable monomer, The carbonyl group ratio of the acrylic copolymer is 22.5% to 26.5%; The proportion of carbonyl groups in the pressure-sensitive adhesive composition is calculated by the following formula 1. [Formula 1] (In the above formula 1, W ｋ is the content (wt%) of any monomer in the total weight of the polymerizable mixture, and M ＣＯ is the molar weight of the carbonyl group (g / mol), and N ｃａｒ、ｋ is the number of carbonyl groups contained in the arbitrary monomer, and M ｋ is the molecular weight (g / mol) of the arbitrary monomer, and n is the number of types of monomers contained in the polymerizable mixture.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the proportion of the carbonyl groups in the acrylic copolymer is 23% to 26%.

3. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the alkyl(meth)acrylate monomer having 1 to 12 carbon atoms comprises a first monomer including an alkyl(meth)acrylate having 1 to 3 carbon atoms and a second monomer including an alkyl(meth)acrylate having 4 to 12 carbon atoms.

4. The pressure-sensitive adhesive composition according to claim 3, wherein the content of the first monomer is 20% by weight to 45% by weight based on the total weight of the polymerizable mixture.

5. The pressure-sensitive adhesive composition according to claim 3, wherein the content of the second monomer is 40% by weight to 75% by weight based on the total weight of the polymerizable mixture.

6. The pressure-sensitive adhesive composition according to claim 1, wherein the aromatic group-containing (meth)acrylate monomer contains an aryloxy group having 6 to 20 carbon atoms.

7. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the aromatic group-containing (meth)acrylate monomer comprises a structure in which an aryl group having 6 to 20 carbon atoms and a (meth)acrylate group are bonded via a polyether segment.

8. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the content of the aromatic group-containing (meth)acrylate monomer is 1 wt % to 15 wt % based on the total weight of the polymerizable mixture.

9. The pressure-sensitive adhesive composition according to claim 1, wherein the content of the carboxyl group-containing crosslinkable monomer is 0.01 wt % to 0.5 wt % based on the total weight of the polymerizable mixture.

10. The pressure-sensitive adhesive composition according to claim 1, wherein the content of the hydroxyl group-containing crosslinkable monomer is 0.5% by weight to 5% by weight based on the total weight of the polymerizable mixture.

11. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the ratio of the weight average molecular weight to the number average molecular weight of the acrylic copolymer is 2.5 to 5.

12. The pressure-sensitive adhesive composition according to claim 1, further comprising at least one additive selected from the group consisting of a crosslinking agent, a silane coupling agent, and an antistatic agent.

13. The pressure-sensitive adhesive composition according to claim 12 , wherein the crosslinking agent is a non-yellowing type isocyanate-based crosslinking agent.

14. A base film; A pressure-sensitive adhesive sheet comprising: a pressure-sensitive adhesive layer disposed on the base film and formed using the pressure-sensitive adhesive composition according to claim 1.

15. A base film; A pressure-sensitive adhesive layer disposed on an upper surface of the base film and formed using the pressure-sensitive adhesive composition according to claim 1; and an anti-reflection layer disposed on the lower surface of the substrate film.

16. A base film; A pressure-sensitive adhesive layer disposed on the base film and formed using the pressure-sensitive adhesive composition according to claim 1; An optical film comprising: a protective layer disposed between the base film and the adhesive layer.

17. The base film is a polyvinyl alcohol film, The optical film of claim 16 , wherein the protective layer is a polymethyl methacrylate-based film.

18. An image display device comprising the optical film according to claim 15.

Images